i'm a rookie

[J.Albers]

As regards moving too much - call YOUR game. If your partner refuses to move or doesn't know how/when to move, let him/her live and die with it. Don't let their inadequacies effect the game you are calling.
Regarding the "illegal screen" - you'll hear it all the time from people who don't know the rule, but just remember one thing: no contact, no foul. If contact does occur you have to determine who initiated it. Refereeing the defense will usually make this call easy.